Test elongate, up to 1.75 mm in length, lenticular, planispiral and with subacute periph­ery in the early stage, later uncoiling and flattened to triangular in section, chambers increasing rapidly in breadth in the early stage, but of nearly constant breadth in the uncoiled stage, sutures gently curved, depressed; wall calcareous, hyaline, single layered: aperture radiate at the dorsal angle. U. Jurassic (Oxfordian to Volgian): USSR: W. Siberia.